The invention relates to a method for cold-rolling of pre-profiled rings and can be preeminently used in the anti-friction bearing industry for the production of internal rings as well as external rings of anti-friction bearings of high accuracy of dimension and accuracy of shape.
Profiling rolling of rings is effected, in part, by hot-forming, whereby depending upon the method, only a limited accuracy of dimension and accuracy of shape can be achieved at relatively high production costs. Especially in the application of the method for the production of anti-friction bearing rings, because of the heating, there result decarbonized peripheral zones which have to be removed by subsequent working steps, which usually are performed by machining. A clear improvement of the accuracy of dimension and accuracy of shape is achieved for certain ring profiles by converting to cold-rolling. With internal, i.e., inward, profiles of rings, and also with some external, i.e., outward, profiles of rings, during the ring expansion phase of the cold-rolling, however, there is the danger that cracks form and defects are generated in the ring cross-section, because during the expansion, there result tangential tensile stresses in the ring, which cause in the ring surface which is not right away acted upon by the roller or rolling mandrel profile a uniaxial state of tensile stress.
Because of the formation of cracks and the generation of defects in the above-mentioned peripheral zones, cold-rolling can be used only to a limited extent for the production especially of anti-friction bearing rings.
According to DE-OS No. 2,607,755, for the cold-profiling of rings, there is proposed a multi-step rolling, whereby in the first steps only the profile, without expanding the diameter, is rolled into the ring. In subsequent steps takes place an even reduction of the thickness over the entire cross-section, which causes an increase of the diameter.
The disadvantage of this cold-rolling method consists in that it requires that the entire reshaping has to be carried out in several steps, whereby each step, in addition to an annealing process, above all requires respective different tool profiles.
Practically, the axial material flow intended in the first step can only be attained by additional apparatus for the limitation of the diameter, which requires relatively high control and finishing expenditures, which in turn has an unfavorable effect upon the operational reliability of the equipment for the execution of the method.
According to DD-PS No. 121,284 it is known to roll pronouncedly internally profiled rings in two steps, in that in the first step a ring workpiece is rolled with an external profile corresponding to the given internal profile, and in a second step, it is finished-rolled as the given internal profile. It is doubtful whether or not this method is realizable.